The present invention relates generally to the pumping of wells such as oil wells, and in particular to an oil well pump assembly having an adjustable production rate capable of long stroke, low stroke per minute pumping rates.
Prior art oil wells have been pumped for many years with a walking beam pump having a relatively large crank and arm assembly providing a sharp acceleration and deceleration of a pump rod. The walking beam arrangement needed a number of reversals per minute of the pump along with a short stroke pumping rod to provide sufficient production. With a walking beam pump, the pumping rod had to be larger than desired since the end of the rod never catches up with the pump in the pumping process and the effective stroke of the rod due to the elasticity of the rod was always less than the actual length of the rod. Also, the crank had to be physically changed in order to change the production rate of the pump.
Improvements were made to the walking beam pumping arrangement by those systems described in U.S. Pat. Nos. 3,744,567, 3,793,904, and 3,807,902, where long stroke pumping assemblies were devised which had counterbalanced weights reciprocally attached to the well pump to move the pumping mechanism and aid the pumping mechanism by the force of gravity on its return stroke. Several disadvantages have presented themselves with the use of the prior art reciprocal well pumps as disclosed in the above referenced patents. First, each of the pumps uses a direct current motor on a spiral (a varying diameter spool) with a hydrostatic drive. The hydrostatic drive does not have a great deal of longetivity and requires a complex set of controls in order to operate the unit. The device as represented by the referenced prior art patents also only controls the speed of the unit. Furthermore, side loads are imposed on the sucker rods of the above-referenced patents.
The present invention has the object of using an oil shear clutch mechanism and brake mechanism to control the operation of a counterbalanced well pump. Such an arrangement permits an alteration in the speed of the unit and also in the dwell time of a unit at the top and the bottom of each stroke, to allow the rod to catch up with the unit and have an effective stroke of the length of the rod. Furthermore, the present invention has an object of eliminating side loads imposed by the sucker rods to extend the life of the unit.
Each of the above advantages is also meant to be included with a pump assembly that has an adjustable production rate readily adjustable externally of the pump assembly. The production rate can be monitored by a main computer by monitoring the sampling and the motor amperage to consistently provide an optimum condition in the performance of the pump. This same computer may be monitoring a number of the pump assemblies of the present invention.
The prior art units also had an energy disadvantage due to the rough accelleration of the unit taking power away from the operation of the unit. The present invention has an energy advantage over the prior art due to the provision of a controlled ramp for accelleration and deceleration of the pump assembly.
The present invention also has the object of providing a pump assembly which is potentially ecologically aesthetic for areas that find objection to large observable well pumps. The present invention may be constructed to have an effective physical size of 5 to 7 feet above ground level, which, in a commercial or residential setting, could locate the unit underneath the parking lot, surrounded by a fence or hedge, within a small attractive housing structure, or in another ecologically aesthetic surrounding. Such a use would also permit the surface real estate to be utilized for something else other than a mere well pumping station. A small pump assembly may also be more amenable to protection against vandalism and the pumps may be situated more closely together, as a series of directional wells to obtain a higher density than prior art well pumps. The present invention also has a much lower weight than the prior art units, which may provide an advantage particularly for off-shore wells where a number of the pumps may have to be attached to a vehicle rig.
Essentially, the present invention provides a simplified, more compact, and potentially more ecologically appealing unit than the prior art.
Additional objects and advantages of the invention, as well as the details of an illustrative embodiment, be more fully understood from the following description and drawings.